Porosity, openness, and exposure: Identification of underlying factors associated with semi-outdoor spaces’ thermal performance and clustering in tropical high-density Singapore

Abstract

• 63 semi-outdoor spaces are characterised in terms of underlying factors (i.e . hypothetical constructs). • Exploratory Factor Analysis (EFA) analyses 11 spatial attributes of semi-outdoor spaces. • EFA reveals 3 underlying factors: volume porosity, perimeter openness & exposure to sky. • Such underlying factors are linked to the microclimate and predicted thermal comfort. • Such underlying factors are associated with how semi-outdoor environments are clustered. The lack of green open spaces undermines the environmental and social quality of tropical highly-dense cities (i.e. raises urban temperatures, limits social interaction). The goal of this study, which focused on environmental aspects, was to identify underlying factors (i.e. hypothetical constructs ) in semi-outdoor spaces within building forms that explain their microclimatic behaviour, thermal comfort levels, and clustering. Sixty-three semi-outdoor spaces in four high/mid-rise building forms of Singapore were studied using microclimatic data collected from field measurements and analysed via inferential statistical methods (e.g., exploratory factor analysis, multivariate regression analysis, and hierarchical clustering analysis). Findings demonstrate: (1) that spatial attributes (i.e. height, depth, void, solid, total frontage, open frontage, area, volume, perimeter, sky view factor, green plot ratio ) are manifestations of three underlying factors: volume porosity (VP) , perimeter openness (PO) and exposure to sky (ES); (2) that VP and PO are significantly associated with air velocity and predicted thermal comfort; and (3) that vertical breezeways appear to be the most thermally comfortable cluster due to high VP and low PO. This study sheds new light on the spatial nature of semi-outdoor spaces, which designers can consider in order to enhance wind movement for promoting thermally comfortable semi-outdoor environments in highly-dense Singapore.